The pressure at which typical gas distribution systems supply gas may vary according to a number of factors. These factors may include, for example, the demands placed on the system, the climate, the source of supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with a predetermined pressure, and at or below a maximum capacity of the end-user appliance. Therefore, process fluid regulators are implemented in these distribution systems in order to ensure that the delivered gas meets the requirements of the end-user facilities. Process fluid regulators are also used to regulate the delivery of liquids to achieve similar functionalities.
A common process fluid regulator includes a regulator body, a control element, and an actuator. The regulator body defines a fluid flow path, a fluid inlet, and a fluid outlet. An orifice is operatively disposed in the body along the fluid flow path between the fluid inlet and the fluid outlet. The fluid flow path extends from the fluid inlet, through the orifice, and to the fluid outlet. The control element shifts to regulate the flow of fluid along the fluid flow path through the orifice. The control element sealingly engages a valve seat defined by the orifice in a closed position, and is spaced away from the valve seat in an open position. In a manner well understood in the art, the actuator is operatively connected to the regulator body and the control element to control the position of the control element relative to the orifice in response to pressure changes in the fluid flow path to maintain a the process fluid pressure within a preselected range, for example, at the fluid outlet.
FIG. 1 shows an isolated and enlarged detail of a typical control element 10 and an orifice 12 in a process fluid regulator. The orifice 12 typically has the form of a circular tube and is secured to a regulator body 14, for example, with outer threads 16 that engage complementary inner threads 17 in the regulator body 14, and surrounds and forms an aperture 18 through which fluid must pass. A valve seat 20 is defined along the upper edge or annular lip of the orifice 12. The control element 10 carries a seal disk assembly, including a seal disk 22 made of resilient sealing material, such as rubber or the like, that is carried in a disk housing 24, which may be, for example, defined by a bottom end of the control element 10. (Directional modifiers, such as up, down, left, and right, are used solely for ease of reference relative to the drawings and do not otherwise limit the scope of the disclosure.) The seal disk 22 includes a mounting portion 25, which preferably has a circular ring shape defining a central aperture. The seal disk 22 may optionally include a central web or disk extending across the central aperture. In the exemplary arrangements shown in the figures, however, the seal disk 22 does not include a central web. The disk housing 24 includes a seating portion 27 in the form of a groove aligned opposite the valve seat 20. The seating portion 27 has a flat rectangular profile. The mounting portion 25 of the seal disk 22 also has a flat rectangular cross section that is complementary to the seating portion 27. The mounting portion 25 fits tightly into the seating portion 27 such that the seal disk 22 is arranged to sealingly engage the valve seat 20 when the control element 10 is moved to a lockup position, i.e., the extreme or maximum closed position of the control element 10 that completely stops fluid flow through the aperture 18 and thus the regulator body.
As best seen in the enlarged detail of FIG. 2, the seating portion 27 of the disk housing 24 has a rectangular cross-section formed by a first side wall 26, a second side wall 28, and a back wall 30. Each of the first and second side walls 26, 28 extends from a first end at an end face 32 of the disk housing 24 to a second end spaced inwardly from the end face 32. The back wall 30 extends from the second end of the first side wall 26 to the second end of the second side wall 28. The side walls 26, 28 are perpendicular to the end face 32, and the back wall 30 is perpendicular to each of the side walls 26, 28. The mounting portion 27 of the seal disk 22 has a similar rectangular profile that fits into the disk housing 24. The seal disk 22 also includes a seal surface 34 that sealingly engages the valve seat 20. The seal surface 34 has a flat face. The mounting portion 27 is complementary to the seating portion 27, having a flat end wall 36 connected to the flat seal surface 34 by side walls 38 and 40. The side walls 38, 40 and end wall 36 of the mounting portion 25 fit against the side walls 26, 28, and the back wall 30 of the seating portion 27, respectively.
As the valve seat 20 compresses and deforms the mounting portion 25 of the seal disk 22 into the seating portion 27 in the lockup position, the seal disk 22 does not remain flat. Rather, as shown graphically by the arrows P, the seal disk 22 deforms unevenly across the rectangular cross section profile of the mounting portion 25 within the seating portion 27. The uneven or non-uniform compression across the profile of the mounting portion 25 may cause the actuation forces necessary to achieve the lock-up position to be higher than necessary.